Diffractive optical element, illumination system comprising the same, and method of manufacturing semiconductor device using illumination system

ABSTRACT

An illumination system including a diffractive optical element (DOE) having an uneven surface that produces an illumination shape. The DOE comprising an uneven surface that produces a multipole illumination shape having angular scope element, wherein the angular scope element is a function of a radius and an angle of the produced multipole illumination shape, and wherein a position of the poles and sizes of the poles in an angular scope vary with a radial scope used in producing the multipole illumination shape, and a method of manufacturing a semiconductor device using the system.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Continuation of U.S. patent application Ser. No.10/874,786 filed on Jun. 22, 2004, now U.S. Pat. No. 7,215,471 and whichclaims priority to Korean Patent Application No. 10-2003-0051118, filedon Jul. 24, 2003, both of which are fully incorporated herein byreference.

BACKGROUND

1. Field of the Invention

The present invention relates, generally, to an illumination system of alithographic apparatus for fabricating a semiconductor device, and moreparticularly, to an illumination system using a diffractive opticalelement (DOE) that provides a multipole illumination.

2. Description of the Related Art

Generally, a lithographic apparatus having an illumination system isused to obtain optimized illumination conditions for forming a finepattern on a semiconductor device. For example, FIG. 1 is a schematicdiagram of a conventional illumination system including a conventionaldiffractive optical element (DOE). Referring to FIG. 1, a conventionalillumination system 100 includes a conventional DOE 10. The DOE 10divides a laser beam 5 projected from a light source (not shown) intoseveral beams, determines the mutual angles of the divided beams, andprovides a multipole illumination shape such as a quadrupole, dipole, orcross-pole. FIG, 2 illustrates a cross-sectional view of theconventional DOE in FIG. 1. Referring to FIG. 2, the DOE 10 is anon-spherical, light-diffracting device equipped with an uneven surface13 formed with a predetermined pitch and depth on a surface of a basematerial 11.

The illumination system 100 produces the quadrupole illumination 15 byprojecting the laser beam 5 through the DOE 10. An inner and outer sigmaσ of the quadrupole illumination 15 are determined when passing througha zoom lens 20. Thereafter, the quadrupole illumination 15 is reflectedby mirrors M1 and M2 and passes through a condenser lens 25, whichcondenses the quadrupole illumination 15. Then, the condensed quadrupoleillumination is directed to a reticle 30 where a mask pattern of thereticle 30 is projected onto a wafer 40 by a projection lens 35.

The advantage of the lithographic apparatus having the aboveillumination system 100 is that light intensity does not decrease sincean aperture, which blocks part of the light, for forming the multipoleis not required. In addition, the poles may be enlarged or reduced, andthe poles radial scope can be changed by the zoom lens 20.

However, once the illumination condition, that is the quadrupole,dipole, cross-pole, etc., is fixed by the DOE 10, a position of thepoles in an angular scope and the relative sizes of the poles cannot beadjusted.

FIG. 3 illustrates the shape of the quadrupole illumination 15 producedby the DOE of FIG. 1. In this case, an illumination shape I(r, θ) can beexpressed by multiplying a radial scope element A(r) by an angular scopeelement C(θ) where (r, θ) are polar coordinates. A(r) is 1 ifr_(inner)<r<r_(outer), otherwise A(r) is 0. C(θ) is 1 if b<θ<c,otherwise C(θ) is 0 (b and c are constants). The position of the polesin the angular scope is fixed at (b+c)/2 independent of r_(inner) andr_(outer). The conventional quadrupole illumination 15 has four poles 15a, 15 b, 15 c, and 15 d, each located in a different quadrant of thexy-plane and being symmetric about the x and y axes.

FIG. 4 shows a shape of a conventional cross-pole illumination 55produced by another conventional DOE. In this case, an illuminationshape I(r,θ) can be expressed by multiplying the radial scope elementA(r) and the angular scope element C(θ), wherein (r,θ) are polarcoordinates. A(r) is 1 only if r_(inner)<r<r_(outer), otherwise A(r) is0. C(θ) is 1 if 0<θ<b and d <θ<π/2, otherwise C(θ) is 0. A ratio ofareas between the poles, b/(π/2−d)=1, is fixed. That is, angles betweenpoles 55 a, 55 b, 55 c, and 55 d are each π/2, and these poles arelocated on the x and y axes.

As a consequence, the illumination shapes formed by the conventionalDOEs depend on C(θ), which is only a function of θ, and has nodependence on r. Thus, even if the radial scope used is changed, theposition of the poles in the angular scope and the relative sizes of thepoles do not change. Accordingly, the conventional DOE has littlepliability. Furthermore, in order to design the optimized illumination,each pole may be required to have a different size. However, it is verydifficult to embody other illumination conditions by using theconventional DOE, which already embodies the optimized illuminationcondition.

Thus, problems in conventional DOEs include the small amount ofpliability due to the fixed illumination mode, difficulty of changing aposition and sizes of the poles, and difficulty of selecting andcombining the illumination conditions.

Therefore, a need exists for a diffractive optical element (DOE) thatproduces a multipole illumination shape and is capable of changing aposition of poles and sizes of the poles of the multipole illuminationshape depending on a radial scope used.

SUMMARY OF THE INVENTION

Exemplary embodiments of the present invention provide diffractiveoptical elements (DOES) that produce a multipole illumination shape andare capable of changing sizes and a position of poles of the multipoleillumination shape depending on a radial scope used.

In an aspect of the present invention, a multipole illumination shape isproduced using a DOE. In another aspect of the present invention, anillumination system for manufacturing a semiconductor device is providedthat is capable of changing the position of the poles in the angulardirection and the sizes of the poles according to the radial scope usedin producing the multipole illumination shape.

According to an exemplary embodiment of the present invention, adiffractive optical element (DOE) is provided that produces a multipoleillumination shape for a lithographic process for a semiconductordevice. The DOE comprises an uneven surface that produces a multipoleillumination shape having an angular scope element that is a function ofa radius and an angle of the produced multipole illumination shape sothat a position and size of poles of the multipole illumination shapevary with the radial scope used.

According to another exemplary embodiment, the DOE having an unevensurface produces a multipole illumination shape in which the size ofeach of the poles change according to the radial scope used. Themultipole illumination shape is a cross-pole illumination shape and asthe radial scope used approaches an origin, the poles located on ay-axis increase in size and poles on an x-axis decrease in size.

According to another exemplary embodiment, the DOE having uneven surfaceproduces a multipole illumination shape having poles in an angular scopein which a position of the poles in the angular scope change accordingto a radial scope used. The DOE having uneven surface may also produce amultipole illumination shape in which the position of poles is closer toan x-axis as the radial scope used approaches the origin.

According to yet another exemplary embodiment of the present invention,an illumination system for manufacturing a semiconductor devicecomprises a light source, a diffractive optical element (DOE) having anuneven surface that divides a light beam output from the light source toproduce a first multipole illumination shape, wherein the DOE determinesthe mutual angles between poles of the first multiple illuminationshape, a variable magnification zoom lens that magnifies the firstmultipole illumination shape from the DOE, an annular aperture, whichselectively allows the magnified first multipole illumination shape topass, thereby producing a second multiple illumination shape, and acondenser lens that condenses the second multipole illumination shapeand directs the second multipole illumination shape to a reticle,wherein the DOE, which produces the first multipole illumination shapehaving both angular and radial directions, used in combination with thevariable magnification zoom lens and the annular aperture to produce thesecond multipole illumination shape that depends on the radial scopeused in producing the first multipole illumination shape.

These and other exemplary embodiments, features, aspects and advantagesof the present invention will become more apparent by the followingdetail description exemplary embodiments when read in conjunction withthe accompany drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a conventional illumination systemincluding a conventional diffractive optical element (DOE).

FIG. 2 illustrates a cross-sectional view of the conventional DOE ofFIG. 1.

FIG. 3 illustrates a shape of quadrupole illumination produced by theconventional DOE of FIG. 1.

FIG. 4 illustrates a shape of cross-pole illumination produced byanother conventional DOE.

FIG. 5 is a schematic diagram of an illumination system formanufacturing a semiconductor device, according to an exemplaryembodiment of the present invention.

FIG. 6 illustrates a first multipole illumination shape output from theDOE of FIG. 5.

FIGS. 7A and 7B illustrate various second multipole illumination shapesresulting from the first multipole illumination shape in FIG. 6,according to another exemplary embodiment of the present invention.

FIG. 8 illustrates a first multipole illumination shape output from aDOE, according to yet another exemplary embodiment of the presentinvention.

FIGS. 9A and 9B illustrate various second multipole illumination shapesresulting from the first multipole illumination shape in FIG. 8,according to still another exemplary embodiment of the presentinvention.

FIG. 10A is an annular illumination shape, according to still yetanother exemplary embodiment of the present invention.

FIG. 10B is a top plane view of a DOE, according to another exemplaryembodiment of the present invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The present invention will now be described more fully with reference tothe attached drawings, in which exemplary embodiments of the presentinvention are shown. This invention may, however, be embodied in manydifferent forms and should not be construed as being limited to theexemplary embodiments set forth herein; rather these exemplaryembodiments are provided so that this disclosure will be thorough andcomplete, and will fully convey the concept of the invention to thoseskilled in the art. In the drawings, the forms of elements areexaggerated for clarity. To facilitate understandings identicalreference numerals have been used for like elements throughout thefigures.

Examples that will be described below are specific examples of multipoleillumination such as quadrupole and cross-pole illumination. However,other illumination modes with more poles may be embodied by adiffractive optical element (DOE) according to the present invention.

FIG. 5 is a schematic diagram of an illumination system formanufacturing a semiconductor device according to an exemplaryembodiment of the present invention. Referring to FIG. 5, a DOE 110having an uneven surface divides light from a laser light source 105into several beams and defines mutual angles of the beams to form afirst multipole illumination shape 115. The multipole illumination shape115 is magnified by passing through a variable magnification zoom lens120. The first multipole illumination shape 115 is then given a uniformintensity by a uniformizing lens 125, and the radial scope of the firstmultipole illumination shape 115 is determined when passing through anannular aperture 130 to form a second multipole illumination shape 116.Thereafter, the second multipole illumination shape 116 is directed to alight-focusing lens 135 and is projected onto a reticle 140 that has amask pattern. Thus, the DOE 110 having an uneven surface, which producesa first illumination shape 115 that is dependent on both the angular andradial scopes, is used in combination with the variable magnificationzoom lens 120 and the annular aperture 130 to produce a second multipoleillumination shape 116 that depends on the radial scope of the firstillumination shape 115.

In order to manufacture the semiconductor device using the illuminationsystem, a substrate (not shown) covered by a photosensitive film isplaced under the reticle 140, and then the mask pattern of the reticle140 is projected onto the photosensitive film. Different illuminationshapes are formed by changing the radial scope of the first illuminationshape 116 by utilizing the combination of the variable magnificationzoom lens 120 and the annular aperture 130. By this process, anoptimized illumination can be selected according to the mask pattern.

The radial position of each pole can be changed by adjusting thevariable magnification zoom lens 120 and the annular aperture 130, and aradial width of each pole can be adjusted by coordinating the variablemagnification zoom lens 120 and the annular aperture 130. In thesecases, the first multipole illumination shape output from the DOE 110 isfixed as a function of the mutual angle.

FIG. 6 illustrates the first multipole illumination shape 115 outputfrom the DOE of FIG. 5, according to an exemplary embodiment of thepresent invention.

As illustrated in FIG. 6, the first multipole illumination shape 115 isrelated to the quadrupole illumination, and shapes of poles 115 a, 115b, 115 c, and 115 d are dependent on the radial scope.

An illumination shape I(r, θ) can be expressed by multiplying a radialscope element A(r) and an angular scope element C(r, θ), wherein (r, θ)are polar coordinates. A(r) is 1 if r_(inner)<r<r_(outer), otherwiseA(r) is 0. C(r, θ) is 1 if ar+b<θ<ar+c, (a, b and C are constants),otherwise C(r, θ) is 0. In this case, a>0, b<c, and an effective poleposition (2ar+b+c)/2 is not fixed but is a function of r. If theseconditions are input into a DOE design program, an uneven surface can bedesigned for dividing beams and determining the beams mutual angles inorder to obtain the first multipole illumination shape 115. A method ofmanufacturing the DOE by applying a DOE design, including etching,machine processing, epoxy injection, injection molding, etc., is wellknown to those skilled in the art. Preferably, Polymethyl methacrylate(PMMA) can be used for the base material of the DOE, and the DOE isformed by etching.

FIGS. 7A and 7B illustrate various second multipole illumination shapesresulting from the first multipole illumination shape 115 in FIG. 6,according to another exemplary embodiment of the present invention.

The second multipole illumination shape in FIG. 7A is obtained byinstalling the DOE capable of producing the first multipole illuminationshape 115 in the illumination system in FIG. 5 and adjusting thevariable magnification zoom lens 120 such that a section of r1 of thefirst multipole illumination shape 115 passes through the annularaperture 130. FIG. 7B is obtained by adjusting the variablemagnification zoom lens 120 such that a section of r2 of the firstmultipole illumination shape 115 passes through the annular aperture130.

When the section r1 of the first multipole illumination shape 115 passesthrough the annular aperture 130, poles 116 a 1, 116 b 1, 116 c 1, 116 d1 are located near the x-axis. However, when the section r2 of the firstmultipole illumination shape 115 passes through the annular aperture130, poles 116 a 2, 116 b 2, 116 c 2, and 116 d 2 are located far fromthe x-axis. Therefore, according to an exemplary embodiment of thepresent invention, the position of each of the poles in the angularscope depends on the radial scope used in producing the illuminationshape.

However, if the conventional quadrupole illumination 15 in FIG. 3 isused in the illumination system of the exemplary embodiment of thepresent invention, the position of the poles does not change. In otherwords, the position of the poles in the conventional quadrupoleillumination does not depend on the radial scope of the illuminationshape used, and the position of the poles does not change regardless ofthe combination of the variable magnification zoom lens 120 and theannular aperture 130.

FIG. 8 illustrates a first multipole illumination shape 215 output froma diffractive optical element (DOE), according to yet another embodimentof the present invention. Referring to FIG. 8, the first multipoleillumination shape 215 is related to cross-pole illumination. The widthsof poles 215 a and 215 c decrease as the radius increases., while thewidths of poles 215 b and 215 d increase as the radius increases. Thisillumination shape, which is expressed as I(r, θ) where (r, θ) are polarcoordinates, has a radial scope element A(r) and an angular scopeelement C(r, θ). A(r) is 1 if r_(inner)<r<r_(outer), otherwise A(r) is0. C(r, θ) is 1 if 0<θ<ar+b and cr+d<θ<π/2, (a,b,c, and d areconstants), otherwise C(r, θ) is 0. In this case, a>0, c<0, and aneffective pole position (ar+b)/(π/2−(cr+d)) between adjacent poles isnot fixed but changed as a function of r.

FIGS. 9A and 9B illustrate various second multipole illumination shapesresulting from the first multipole illumination shape in FIG. 8according to still another exemplary embodiment of the presentinvention.

The second multipole illumination shape in FIG. 9A is obtained byinstalling a DOE capable of producing the first multipole illuminationshape 215 in the illumination system in FIG. 5 and by adjusting thevariable magnification zoom lens 120 such that a section of r1 of thefirst multipole illumination shape 215 passes through the annularaperture 130. The second multipole illumination shape of FIG. 9B isobtained by adjusting the variable magnification zoom lens 120 such thata section of r2 of the first multipole illumination shape 215 passesthrough the annular aperture 130.

When the section of r1 of the first multipole illumination shape 215passes through the annular aperture 130, poles 216 a 1 and 216 c 1located on the y-axis are larger than poles 216 b 1 and 216 d 1 locatedon the x-axis. However, when the section r2 of the first multipoleillumination shape 215 passes through the annular aperture 130, thepoles 216 a 2 and 216 c 2 located on the y-axis are smaller than thepoles 216 b 2 and 216 d 2 located on the x-axis. Therefore, the relativesizes of the poles change according to the radial scope of the firstmultipole illumination shape 215 passing through the annular aperture130.

However, if the conventional cross-pole illumination 55 in FIG. 4 isused in the illumination system of the exemplary embodiments of presentinvention, the relative sizes of the poles do not change because thepoles are independent of the radial scope used of the illuminationshape. In other words, the size of the poles of the conventionalcross-pole illumination 55 does not change regardless of the combinationof the variable magnification zoom lens 120 and the annular aperture130.

FIG. 10A is an annular illumination shape, and FIG. 10B is a top planeview of a DOE, according to still yet another exemplary embodiment ofthe present invention.

In order to manufacture a DOE that will produce the annular illuminationshape in FIG. 10A, an equation reflecting this illumination is inputinto the DOE design program. That is, the annular illumination shape isexpressed as I(r) where I(r) is 1 if r_(inner)<r<r_(outer), otherwiseI(r) is 0. If this equation is input in the DOE design program, anuneven surface as shown in FIG. 10B is obtained. If the design programis used to form the uneven surface in a base material, e.g., polymethylmethacrylate (PMMA), of the DOE, the annular illumination shape of FIG.10A is produced. This method is well known to those skilled in the art.Thus, the DOE according to the present invention, based on theexplanations with reference to FIGS. 6 and 8, can also be manufactured.

A DOE according to an exemplary embodiment of the present inventiongenerates a multipole illumination shape with poles that have a widththat is dependent on the radial scope used in producing the multipoleillumination shape. A DOE, according to another exemplary embodiment ofthe present invention, generates a multipole illumination shape thatincludes poles with varying sizes and positions that are dependent onthe radial scope. Thus, it is noted that it is not a simple modificationin designing. Also, it is preferable that the DOE according to exemplaryembodiments of the present invention be used in the illumination systemof a lithographic apparatus. However, the DOE may also be used inillumination systems such as cameras and observation apparatus.

The positions and the relative sizes of the poles are controlled by thecombination of the variable magnification zoom lens, the annularaperture, and a DOE according to the exemplary embodiments of thepresent invention. This feature is very useful for enlarging thelithographic apparatus and reducing the amount of trial and error whendesigning an optimal illumination condition. A process latitude of thelithographic apparatus is also improved.

While the present invention has been particularly shown and describedwith reference to exemplary embodiments thereof, it will be understoodby those of ordinary skill in the art that various changes in form anddetails may be made therein without departing from the spirit and scopeof the present invention as defined by the following claims.

1. A method of manufacturing a semiconductor device, the methodcomprising: providing a substrate coated with a photosensitive film; andusing a laser light source to project a mask pattern of a reticle abovethe substrate onto the photosensitive film, wherein a diffractiveoptical element (DOE) has an uneven surface that produces differentlyshaped multipole illuminations depending on a radial scope used, whereina multipole illumination shape is used to project the mask pattern ontothe substrate, and wherein the multipole illumination shape has anangular scope that depends on a radius and an angle of the producedmultipole illumination shape.
 2. The method of manufacturing thesemiconductor device of claim 1, wherein the multipole illuminationshape includes poles of various sizes, and wherein each of the poles isa different size.
 3. The method of manufacturing the semiconductordevice of claim 1, wherein the multipole illumination shape includespoles, and wherein a position of the poles within an angular scopevaries depending on a radial scope used.
 4. A method of manufacturing asemiconductor device, the method comprising: providing a substratecoated with a photosensitive film; and using a laser light source toproject a mask pattern of a reticle above the substrate onto thephotosensitive film, wherein a diffractive optical element (DOE) has anuneven surface that produces a multipole illumination shape I(r,θ)expressed by multiplying a radial scope element A(r) and an angularscope element C(r,θ), wherein r and θ are a radius and an angle of polarcoordinates, respectively, and θ is dependent on r, and wherein aposition of the poles and sizes of the poles in an angular scope varywith a radial scope used in producing the multipole illumination shape.5. The method of manufacturing the semiconductor device of claim 4,wherein the size of each of the poles varies according to the radialscope used.
 6. The method of manufacturing the semiconductor device ofclaim 5, wherein the multipole illumination shape is a cross-poleillumination shape, and wherein the poles located on a y-axis increasein size and the poles on an x-axis decrease in size as the radial scopeused in producing the multipole illumination shape approaches an origin.7. The method of manufacturing the semiconductor device of claim 5,wherein A(r) is 1 if r_(inner)<r<r_(outer), otherwise A(r) is 0, andC(r, θ) is 1 if 0<θ<ar+b and cr+d<θ<π/2, otherwise C(r,θ) is 0, a>0 andc<0, and a size ratio (ar+b)/(π/2−(cr+d)) between adjacent poles is afunction of r.
 8. The method of manufacturing the semiconductor deviceof claim 4, wherein the position of the poles in an angular directionvaries according to the radial scope used.
 9. The method ofmanufacturing the semiconductor device of claim 8, wherein the positionof the poles are closer to an x-axis as the radial scope used approachesan origin.
 10. The method of manufacturing the semiconductor device ofclaim 8, wherein the multipole illumination shape is given by I(r, θ),which is expressed by multiplying a radial scope element A(r) and anangular scope element C(r, θ), where (r, θ) are polar coordinates, andwherein A(r) is 1 if r_(inner)<r<r_(outer), otherwise A(r) is 0, andC(r, θ) is 1 if ar+b<θ<ar+c, otherwise C(r, θ) is 1, a>0 and b<c, and apole position of the poles (2ar+b+c)/2 is a function of r.
 11. Themethod of manufacturing the semiconductor device of claim 4, wherein theillumination shape is quadrupole or cross-pole.
 12. An illuminationsystem for manufacturing a semiconductor device, the system comprising:a laser light source projecting a mask pattern of a reticle above asubstrate onto a photosensitive film; a diffractive optical element(DOE) having an uneven surface that produces differently shapedmultipole illuminations depending on a radial scope used, wherein amultipole illumination shape is used to project the mask pattern ontothe substrate, and wherein the multipole illumination shape has anangular scope that depends on a radius and an angle of the producedmultipole illumination shape.
 13. The illumination system of claim 12,wherein the multipole illumination shape includes poles of varioussizes, and wherein each of the poles is a different size.
 14. Theillumination system of claim 12, wherein the multipole illuminationshape includes poles, and wherein a position of the poles within anangular scope varies depending on a radial scope used.